Needleless injection device (1) comprising a gas generator (2), a reservoir (5) in the form of a glass tube (6) closed by an upstream stopper (7) and a downstream stopper (8) between which a liquid active principle (9) is accommodated, and an injection nozzle (15) equipped with a receptacle (19) and with at least one peripheral injection conduit (20), said tube (6) having, at one of its ends, a flange (4) via which it is in contact with said nozzle (15). The main feature of this needleless injection device (1) is that the tube (6) has a cylindrical inner channel with an upstream part (21) which is continued by a downstream part (22) of smaller diameter, said downstream part (22) being surrounded by said flange (4) and opening into the receptacle (19).
